The present invention pertains to sphygomanometers for measuring blood pressure in humans.
In general, sphygomanometers include an elongate, pliable, inflatable band which is adaped to be wrapped around and circumferentially tensioned about the upper arm of a patient. A manual air pump is connected to an inflatable bladder carried within the band, and a pressure gage is similarly connected to the bladder to measure the air pressure therewithin at any instant. Typically the band is provided with fastening means so that it may be secured in place about the patient's arm under a predetermined initial tension. By thereafter inflating the band bladder, circumferential pressure on the patient's arm is increased to a measured level which impedes the flow of blood through the arteries of the arm at the location of the sphygomanometer band.
By varying the amount of air pressure applied to the bladder of the band, and simultaneously listening to the sound of the blood as it is pumped by the heart through the arteries of the arm by a stethoscope, it is possible to measure the systolic and diastolic blood pressures of the patient. The systolic pressure corresponds to the arterial blood pressure at which blood is just barely being pumped through the artery, at the point of constriction caused by the inflated arm band. This pressure level is identified by a unique "tapping" sound made by the blood as it is pumped through the restricted artery, with the corresponding blood pressure being read from the pressure gage associated with the inflatable sphygomanometer band at the instant "tapping" sound occurs. The systolic blood pressure corresponds to the relatively higher blood pressure measurement. The lower, diastolic pressure, is ascertained by releasing air from the inflated band to decrease the amount of constriction applied to the patient's arm, and monitoring the blood flow sounds by the stethoscope, noting the pressure at which "tapping" sounds become muffled. The pressure at this point corresponds to the diastolic blood pressure.
The levels of these blood pressures are important in monitoring the physical condition of the patient, and more particularly diagnosing dangerously high or low blood pressure levels. The present invention is particularly concerned with the ability of the patient to measure his own blood pressure, without the assistance of medical personnel or other attendants. It is now generally recognized that blood pressure, and more particularly extremes thereof, are significant contributing factors to heart disease. Moreover, it is believed that transitory periods of high blood pressure in a patient can be controlled or lowered by the conscious action of the patient himself, if he is aware of a temporary high blood pressure condition. Typically, medicine can be taken, or the patient can consciously relax, take a rest or otherwise ameliorate the activity which has induced the high blood pressure.
This ability of the patient to control his own activity in response to temporary blood pressure conditions, has resulted in the recommendation by doctors and other medical authorities, that the patient be equipped with his own sphygomanometer and stethoscope in order to monitor his blood pressure at home or at work, without requiring frequent trips to the doctor's office or hospital. This allows a more effective use of relaxation techniques for reducing temporary excesses of blood pressure.